Gas generator compositions

ABSTRACT

1. A gas generator composition consisting essentially of a fuel selected from CELLULOSE ACETATE, NITROCELLULOSE AND MIXTURES THEREOF; AN ENERGETIC PLASTICIZER SELECTED FROM THE GROUP CONSISTING OF TRIMETHYLOLETHANE TRINITRATE, PENTAERYTHRITOL TRINITRATE, DIETHYLENE GLYCOL DINITRATE AND MIXTURES THEREOF; A NONENERGETIC PLASTICIZER SELECTED FROM THE GROUP CONSISTING OF HYDROXYPROPYLGLYCEROL, DIETHYL PHTHALATE AND DIBUTYL PHTHALATE; A STABILIZER SELECTED FROM THE GROUP CONSISTING OF N-methyl-pnitroaniline, ethyl centralite and resorcinol; and A BALLISTIC MODIFIER SELECTED FROM THE GROUP CONSISTING OF DIBUTYL TIN MALEATE, LEAD SALICYLATE, MANGANESE DIOXIDE, STANNIC OXIDE, ZINC CARBONATE, MONOBASIC CUPRIC SALICYLATE, MONOBASIC LEAD BETA RESORCYLATE, MONOBASIC LEAD SALICYLATE AND MIXTURES THEREOF.

United States Patent Crescenzo et al.

[ Feb. 1, 1972 [54] GAS GENERATOR COMPOSITIONS [72] Inventors: Frank G. Crescenzo; Robert L. Dow, both of China Lake, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: Apr. 16, 1965 [21 Appl. No.: 450,249

Primary ExaminerBenjamin R. Padgett AttqrneyGeorge J. Rubens, Peter H. Firsht and Victor C. Muller EXEMPLARY CLAIM l. A gas generator composition consisting essentially of a fuel selected from cellulose acetate, nitrocellulose and mixtures thereof;

an energetic plasticizer selected from the group consisting of trimethylolethane trinitrate. pcntaerythritol trinitrate. diethylene glycol dinitrate and mixtures thereof a nonenergetic plasticizer selected from the group consisting of hydroxypropylglycerol. diethyl phthalate and dibutyl phthalate;

a stabilizer sedected from the group consisting of N- methyl-p-nitroaniline, ethyl centralite and resorcinol; and

a ballistic modifier selected from the group consisting of dibutyl tin maleate, lead salicylate, manganese dioxide. stannic oxide, zinc carbonate. monobasic cupric salicylate, monobasic lead beta resorcylate. monobasic lead salicylate and mixtures thereof.

8 Claims, No Drawings GAS GENERATOR COMPOSITIONS The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to solid propellant compositions and in particular to an improved gas generator composition.

In recent years a considerable amount of research has been expended on improving the performance characteristics of solid propellants. Many compounds have been found which have the ability to change the burning properties of propellants, which are among their most important. Experiences gained from utilizing solid propellants have shown that the burning rate is influenced by the pressure of the gas in contact with the burning surface, by the temperature of the unburned propellant, by the velocity of the gas past the burning surface, and finally, by the composition of the propellant. The present invention provides a new propellant composition which is useful over a wide environmental range and which meets exacting requirements for auxiliary power sources in guided missiles.

It is therefore an object of the present invention to provide a propellant composition for modern missile systems.

Another object is to provide a propellant composition capable of being formed in a wide variety of grains and shapes, all with improved chemical and physical properties.

A further object is to provide a propellant composition which is relatively simple to manufacture and safe to handle.

Other objects, features and many of the attendant advantages of this invention will become readily appreciated as the same become better understood by reference to the following detailed description.

The present invention is for a gas generator composition comprising a fuel consisting of cellulose acetate, nitrocellulose, and mixtures thereof, either in commercial or plastisol form; an energetic plasticizer selected from the group consisting of trimethylolethane trinitrate (TMETN), pentaerythritol trinitrate (PETriN), diethylene glycol dinitrate (DEGN), and mixtures thereof; a nonenergetic plasticizer selected from the group consisting of hydroxypropylglycerol, diethyl phthalate, and dibutyl phthalate; a stabilizer for nitrate esters such as N- methyl-p-nitroloanilirie and resorcinol and a ballistic modifier selected from the group consisting of dibutyl tin maleate, stannic oxide, zinc carbonate, lead salicylate, manganese dioxide, monobasic cupric salicylate, monobasic lead beta resorcylate, monobasic lead salicylate and mixtures thereof.

The solid grain utilizing the plastisol form of fuel ingredients is generally prepared by mixing the components together at room temperature in a sigma blade mixer for about 30 minutes until a homogeneous mixture results. The mixture is then cast in a rocket motor tube or casing and oven cured at temperatures between 120 and 180 F. for about 2 hours. The components, except the ballistic modifier, may also be mixed into a paste and rolled during which process the ballistic ingredient is added to the moist sheet of propellant. The ballistic modifier is worked in during the rolling mill action forming a rubbery sheet of modified propellant. The mixture may also be extruded into various grain forms.

The plastisol cellulose acetate was prepared by first dissolving pulverized cellulose acetate in a quantity nitromethane to form a lacquer. While this process is proceeding, a mixture of petroleum sulfonate emulsifying agent sold under the trade name Petromix, and water was poured into a colloid mill. The mill was put into operation and the lacquer made in the first step was slowly added. The mill was operated until an emulsion formed which was agitated for about 30 minutes in water at approximately 100 F. The wet plastisol material was then passed through a ZOO-mesh stainless steel screen and into a centrifuge. The material was vacuum dried at 180 F. for about 2 days. A dry, lump-free, plastisol cellulose acetate results which is free-flowing and has a reduced static charge.

Plastisol nitrocellulose into tiny, dense, spheres (of the order of microns in diameter). The method is disclosed in patent application, Ser. No. 761,448, filed Sept. 16, 1958, and is as follows: gramsof nitrocellulose (12.6% N), 1.2 grams of ethyl centralite and 1.4 liters of nitromethane placed in a flask and stirred vigorously until dissolution occurred. Stirring continued for an additional 10 minutes to insure homogeniety. To the resulting lacquer was added l9.2 grams of petroleum sulfonate emulsifying agent for nitrocellulose in about 900 ml. of water. This mixture was circulated through a colloid mill for about 10 minutes, then the resulting emulsion was drained from the mill into about 30 liters of water and stirred for about l5 minutes until a nitrocellulose precipitate formed which was filtered from the liquid, washed in hexane, dried for about 16 hours and siftedthrough a ZOO-mesh screen.

The following are representative examples of the preferred compositions preparedin accordance with this invention and should not be considered as limiting it.

EXAMPLE I Ingredients Percent by weight Plastisol cellulose acetate 45.0 Metriol trinitrate (TMETN) 44.0 Dibutyl phthalate 5.0 Dibutyl tin maleate 5.0 N-methyl-p-nitroaniline l.0

Following is data for the above composition: Measured heat of explosion 538 caL/g. Temperature coefficient at 70 F. and [000 p.s.i.a. 0.704 Pressure exponent, rt, 70 F. Pressure interval: 4002,000 0.66

EXAMPLE ll Ingredients Percent by weight Cellulose acetate 45.5 Trimethylolelhane trinitrate 47.5 Resorcinol L0 Dibutyl tin maleute 3.0 Monobusic lead fl-resorcylate 3.0

EXAMPLE lll Ingredients Percent by weight Plastisol cellulose acetate 35.0 Trimethylolethane trinitrate 46.0 Hydroxypropylglycerol l3 .0 N-melhyLp-nitroaniline 1.0 Dibutyl tin maleate 5.0

Firing results: Heat of explosion 577 caL/g. Pressure exponent, 70 F. 0.65 Burning rate in./sec. at 550 p.s.i. (70 F.) 0.034 at 820 psi. (l30 F.) 0.05]

EXAMPLE 1V Ingredients Percent by weight Plastisol Nitrocellulose [2.6% N) 30.4 Cellulose acetate 7.6 Ethyl centralite 2,0 Pentaerylhritol trinitrate 39.9 Dibutyl phthalate 16.6 N-methyl-p-nitroaniline [.0 Zinc carbonate 2.5

The followifls e Y' lowering both the pressure exponent and temperature coefficient. The use of more than one of the modifiers, namely, Measured heat of exploslon 660 caL/g. Tcmpemm m7o p dlbutyl tln maleate, zlnc carbonate, stanmc oxide, lead saland 500 si. -3 icylate, manganese dioxide, monobaslc cupric salicylate, F monobasic lead beta resorcylate, monobasic lead salicylate Pressure lnterval: 400-950 0.43

9504.000 0.81 usually has an addltlve effect. Table l below ls a comparison of the burning data of an unmodified gas generator composition with those of the present invention.

EXAMPLE V 10 TABLE I lngredims Percent by weight Unmodified v. modified propellant P i T t l l of I'GSSU! em en] 11 Plastisol Nitrocellulose (12.6% N) 30.4 exponent? g gg 22 13;; Cellulose acetate 7.6 15 v Ethyl centralite 2.0 S D (u m 8. 2% :33

. xamp e v fsj gs' 7 0 Example III 0 65 577 1 Y P f e H "0 Example 1V. 0 81 0. all 060 t -l Example v. 0. 45 0.20-0.27 27 Stannlc oxlde Example V1,- 0. 22 0. 24-0 12 644 ExampleVII 0.04 0.16 0 15 037 Data for the above composition 1 At 70 F., SOD-2,000 p.s.i.a. is as renews; *Plastlsol cellulose acetate, 45.0; Metrial trinitl'ate, 44.0; Dibutyl Measured f l i t l 627 phthalate, 5.0; Methyl methacrylate, 5.0; N-methyl-p-rlltroaniline 1.0. Temperature Coefficient at 70 F. and 1500 psia 0.29 W v I i V e MMHZQQQP 5 o I o e E 4 2'65 The use of metallic tm and organotln salts such as dlbutyl tln Burning me 1045 and maleate in the formulation generally aids in producing gas 70F..in./sec. generator formulations with slgnlficantly lower pressure ex- 5 ponents and also modifies burning characteristics by produc- Strand burning 0.11

30 mg composltlons wlth less free carbon particles m the exhaust stream. The or anotin com ounds are reduced to molten EXAMPLE vl 5 metallic tln during the combustlon process and apparently mgrediems Percemby weigh! trap solldsnn the exhaust stream. One sample of the combustlon residue analyzed was found to be 1 mole of on to l 1 Plasfisol nitrocellulose mm, N) 304 moles of :arbon with a small amount of unldentlfied organlc Cellulose acetate 7.6 compoun S. Ethyl centralite 2.0 The use of copper and lead compounds generally lower the W 'Y "inilrm :2: temperature coefficient but some decrease is noted in the pressure exponent. N-methyl-p-nltroanlllne 1.0 Dibmyl fin maleae 50 4 Obviously many modifications and variations of the present invention are possible in the light of the above teachings. it is Damfunhe above composition therefore to be understood that within the scope of the apis as follows: pended claims the invention may be practiced otherwise than Measured heat of explosion, cal/g. as ifi lly d ib d Temperature Coefficient at 70 F. and 1000 psia 8.24 w s claimed 1500psia vl2 Pressure exponentat70"F.,n 1. A gas generator composition consisting essentially of a Pressure {gggjggg fuel selected from Burning me 35 53351" cellulose acetate, nitrocellulose and mixtures thereof; 70" F., in./sec. an energetic plasticizer selected from the group consisting 210 2"; of trimethylolethane trinitrate, pentaerythritol trinitrate,

" diethylene glycol dinitrate and mixtures thereof;

a nonenergetic plasticizer selected from the group consist- EXAMPLE v1 ing of hydroxypropylglycerol, diethyl phthalate and dibutyl phthalate; ingredients Percent by weight a stabilizer selected from the group consisting of N-methylp-nitroaniline, ethyl centralite and resorcinol; and Plastisolnitrocellulcsc(116% N) 30.4 a ballistic modifier selected from the group consisting of Cellulose acetate 7.6 dibutyl tin maleate, lead salicylate, manganese dioxide, Ethyl ccnlmlllc stannic oxide, zinc carbonate, monobaslc cupric sal- Pcntaerythrltol trlnltrate 38.8 l b l d b l mbmyl phthalate In my ate, mono 3 816 ea eta resorcy ate, monobaslc lead N-methyl-p nilroaniline 1.0 sallcylate and 'mlxtures thereof. Dibutyl tin maleate 2. A gas generator composition consisting of the following Stannic oxide 2.5

Ingredients Percent by weight Data for the above composition is as follows: Measured heat of explosion, caL/g. 637 Plastisol cellulose acetate 45.0 Temperature Coefficient at F. and I000 psia 0.1 r mcthylolcthane trinitl'ate 44.0 2000 psia I 0J5 Dibutyl phthalate 5.0 Pressure exponent at 70 F., n Dibutyl tin maleate 5.0 Pressure interval: l.600-2,250 0.04 70 N-methyl-p-nitroaniline 1.0,

The ballistic modifier added to the gas generator composi- 3. A gas generator composition consisting of the following tions changed the burning rate by (l) lowering the pressure exponent, (2) lowering the temperature coefficient, (3)

Ingredients Percent by weight Cellulose acetate 45.5 Plastisol nitrocellulose 30.4 Trimethylclethane trinitrate 47.5 Cellulose acetate 7.6 Resorcinol L Ethyl centralite 2.0 y main" 5 Pentaerythritol trinitratc 37.0 Monobasic lead fi-resorcylate 3.0. Dibmy] m m 7 N-methyl-p-nitmuniline l.0

Stannic oxide 5.0.

4. A gas generator composition consisting of the following 10 7. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol cellulose acetate 35.0 Ingredients pcrcem by weigh Trimethylolethane t'rinitrate 46.0 Plastisol nitrocellulose 30.4 N -methyl -p mtroamlme 1.0 ceuulose Bane 7b Dibutyl tin \fnaleate 5.0. Ethyl mum: Lo Pentaerythritol trinitrate 38.8 Dibutyl phthalate 15.2 A r o c o h 1 N-methyl-p-nitroaniline 1.0 5 gas gene ator c mp0 won on ting f t e fol 0 mg BMW in mime V a V V 245 Stannic oxide 2.5 Ingredients I Percent by weight nilmcellubse 304 8. A gas generator composition consisting of the following Cellulose acetate 7.6 Ethyl centralite 2.0 Pentaerythritol trinitrate 39.9 Ingredients Percent by weight Dibulyl phthalate 16.6 N'methyl-p-nitroaniline 1.0 Zinc carbonate 25 Plastisol cellulose acetate 35.0 Trimethylolethane trinitrate 46.0 Dibutyl tin maleate 5.0 0 Hydroxypropylglycerol l3.0 6. A gas generator composition consisting of the following m my -pma il n 1.0.

ingredients Percent by weight 

1. A GAS GENERATOR COMPOSITION CONSISTING ESSENTIALLY OF A FUEL SELECTED FROM CELLULOSE ACETATE, NITROCELLULOSE AND MIXTURES THEREOF; AND ENERGETIC PLASTICIZER SELECTED FROM THE GROUP CONSISTING OF TRIMETHYLOLETHANE TRINITRATE, PENTAERYTHRITOL TRINITRATE, DIETHYLENE GLYCOL DINITRATE AND MIXTURES THEREOF; A NONENERGETIC PLASTICIZER SELECTED FROM THE GROUP CONSISTING OF HYDROXYPROPYLGLYCEROL, DIETHYL PHTHALATE AND DIBUTYL PHTHALATE; A STABILIZER SELECTED FROM THE GROUP CONSISTING OF NMETHYL-P-NITROANILIENE, ETHYL CENTRALITE AND RESORCINOL; AND A BALLISTIC MODIFIER SELECTED FROM THE GROUP CONSISTING OF DIBUTYL TIN MALEATE, LEAD SALICYLATE, MANGANESE DIOXIDE, STANNIC OXIDE, ZINC CARBONATE, MONOBASIC CUPRIC SALICYLATE, MONOBASIC LEAD BETA RESORCYLATE, MONOBASIC LEAD SALICYLATE AND MIXTURES THEREOF.
 2. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol cellulose acetate 45.0 Trimethylolethane trinitrate 44.0 Dibutyl phthalate 5.0 Dibutyl tin maleate 5.0 N-methyl-p-nitroaniline 1.0.
 3. A gas generator composition consisting of the following Ingredients Percent by weight Cellulose acetate 45.5 Trimethylolethane trinitrate 47.5 Resorcinol 1.0 Dibutyl tin maleate 3.0 Monobasic lead Beta -resorcylate 3.0.
 4. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol cellulose acetate 35.0 Trimethylolethane trinitrate 46.0 Hydroxypropylglycerol 13.0 N-methyl-p-nitroaniline 1.0 Dibutyl tin maleate 5.0.
 5. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol nitrocellulose 30.4 Cellulose acetate 7.6 Ethyl centralite 2.0 Pentaerythritol trinitrate 39.9 Dibutyl phthalate 16.6 N-methyl-p-nitroaniline 1.0 Zinc carbonate 2.5.
 6. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol nitrocellulose 30.4 Cellulose acetate 7.6 Ethyl centralite 2.0 Pentaerythritol trinitrate 37.0 Dibutyl phthalate 17.0 N-methyl-p-nitroaniline 1.0 Stannic oxide 5.0.
 7. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol nitrocellulose 30.4 Cellulose acetate 7.6 Ethyl centralite 2.0 Pentaerythritol trinitrate 38.8 Dibutyl phthalate 15.2 N-methyl-p-nitroaniline 1.0 Dibutyl tin maleate 2.5 Stannic oxide 2.5
 8. A gas generator composition consisting of the following Ingredients Percent by weight Plastisol cellulose acetate 35.0 Trimethylolethane trinitrate 46.0 Dibutyl tin maleate 5.0 Hydroxypropylglycerol 13.0 N-methyl-p-nitroaniline 1.0. 